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6.8 SPC win 748
reelserious
Member Posts: 11 ✭✭
I have a bunch of Win 748 left over. does anyone have any idea of a load for 6.8spc with this. I can't find any data anywhere with this powder. I would appreciate knowing where to begin without blowing myself up. This is the only rifle round I load now.
Comments
I think the reason you can't find any data is because the powder is too slow for use with this cartridge and the recommended bullets. That means that the velocities will be low for the quantity of powder loaded. Now, that doesn't mean you couldn't try some loads but you'll find that the powder will not all burn and there will be a significant amount of fouling. You need a faster powder.
Re-7
IMR-4198
Ramshot X-Terminator
Best.
I'm a little confused here with this myself. I was thinking, wasn't Win 748, Winchesters small case powder? And 760 the standard capacity/larger case powder? I see Win 748 used in some other small/medium case applications i.e. 30 Rem, 250 Savage, 6mm PPC. I mean for burn rate it's about right with BL-C(2) and H335.
Not that I think it's the greatest powder out there but I would think it would kind of fit for loading a 6.8 SPC. And no, I didn't find any 6.8 SPC data for it.
This information can be confusing simply because we are all so used to using just the data published in reloading manuals and information supplied by the powder manufacturers. Now before everyone starts screaming, let me state flat out that reloading manuals and the powder manufacturers are two of the greatest resources that a shooter/reloader can have at their fingertips. I use dozens of the manuals and I am in contact with powder manufacturers weekly so I'm not demeaning their contributions at all.
The problem comes from not being able to refine the data and understand what actually takes place in the barrel when you set off the primer. Chronographs are often a big help but even they can't tell the whole story, only a part. But it is a part that gets our attention, lower velocities by comparison from a 100% case volume of powder.
"Homer Powley defined the relationship between muzzle velocity and barrel length, as one giving muzzle velocity (v) as a function of charge weight C, bullet weight B and expansion ratio (R). Here the expansion ratio is defined as the ratio of the barrel volume plus cartridge volume (total volume of the gun) to the cartridge volume." (http://www.loadammo.com/Topics/October05.htm)
The larger diameter of the bullet, .277" in this example, in relationship to the volume of the cartridge case and the volume of the barrel is a little out of whack. We aren't able to generate enough pressure with WW-748 in this situation. There are two ways to change the pressure:
Use a longer, heavier bullet which takes up more powder space.
Switch the powder to one that creates energy faster.
The peak pressure needs to occur in a shorter period of time and distance. In the instance of WW-748, its burning rate is created by the granular surface area with the deterrents and graphite applied to that surface that keeps it balanced. However, this balance is not in range of the expansion ration needed to burn all the powder in the barrel while providing relative pressure or velocity in relationship to the case volume. The powder is too slow.
WW-748 does work well in cartridges such as the 22-250 but with lighter bullets only. It doesn't work as well with the .243 or .260 as it does with the .308 and light bullets. It's not that it can't be used, there are better powders.
Best.